A touch panel includes two substrates opposed to each other and resistive films provided on opposed inner surfaces of the substrates. Further, on both ends of each of the resistive films, electrodes are provided. Such a touch panel operates on principles that power is externally supplied to both the resistive films alternately and an electrical signal corresponding to a position where the two resistive films are brought into contact with each other by a touch event is outputted to the outside via the electrodes to which no power is supplied. Usually, in view of the output of signals to the outside, each of the electrodes extends to a position corresponding to the position of a connecting part of the touch panel, and the ends of the individual electrodes are brought together in one place to facilitate connection between the electrodes and a lead wire of FPC (flexible printed circuit).
However, the touch side substrate is formed from a resin sheet and the electrodes are formed of a silver paste, so it is hard to say that the electrodes themselves have high strength. Further, conducting wires of the lead wire are connected to the electrodes, respectively, with a conductive paste having a low fixing power, and are held between the touch side substrate and the non-touch side substrate. Therefore, if a slightly large force is applied to the lead wire, there is a possibility that the conducting wire is broken at the connecting part. For this reason, the touch panel needs to be handled very carefully. Furthermore, when the touch panel is frequently touched by a sharp pen point, the touch panel may need to be replaced with a new one due to the damage on the surface of the touch side substrate. In this case, the maintenance by users becomes complicated.
In order to solve these problems, Japanese Patent Laid-open No. H9-50731 discloses a touch panel in which FPC is not directly drawn out from the side face thereof. Hereinbelow, the touch panel in the above identified publication is to be explained.
FIG. 10 is a partial longitudinal sectional view of a main part of the touch panel in which FPC is not directly drawn out from the side face thereof, and FIG. 11 illustrates the structure of electrodes. As shown in FIGS. 10 and 11, a touch side substrate 2, designed to be directly touched by an operator's finger, is formed from a transparent insulating member having a certain degree of flexibility such as, for example, a polyethylene terephthalate (PET) film. On the lower surface of the touch side substrate 2, there is provided a rectangular resistive film 2a of ITO (indium tin oxide) or the like formed by, for example, sputtering or vacuum deposition.
On the other hand, a non-touch side substrate 3 is provided so as to be opposed to the touch side substrate 2. Such a non-touch side substrate 3 is formed from a glass plate, a resin plate, or the like. On the upper surface of the non-touch side substrate 2, there is provided a rectangular resistive film 3a that is similar to the resistive film 2a provided on the touch side substrate 2. Further, at the periphery of the non-touch side substrate 3, there are provided through-holes 4a, 4b, 4c, and 4d to constitute a connecting part 5.
At opposite sides of the resistive film 2a in the Y direction, there are provided band-like electrodes 2b and 2c. At opposite sides of the resistive film 3a in the X direction, there are provided band-like electrodes 3b and 3c. These band-like electrodes 2b, 2c, 3b and 3c are formed using a silver paste. Each of the electrodes 2b, 2c, 3b, and 3c extends to a position corresponding to the position of the connecting part 5 provided at the end of the touch panel 1.
Into the through-holes 4a, 4b, 4c, and 4d, a conductive paste 8 such as a silver paste is injected, and then recessed (female) fittings 7 (see FIG. 12) or convex (male) fittings 13 (see FIG. 13) are embedded in the through-holes to electrically connect to the electrodes 2b, 2c, 3b, and 3c, thereby the connecting part 5 can be obtained for connecting with an external devices.
In the above-described configuration, electrical signals from the resistive films 2a and 3a can be easily taken out from the lower side of the touch panel 1 not by drawing out a lead wire from the side face of the touch panel 1 but by connecting other convex (male) fittings such as connector pins 12 to the recessed (female) fittings 7 or connecting other recessed (female) fittings to the convex (male) fittings 13, therefore it is possible to prevent the possibility of breaking of wires inside of the touch panel and to be extremely easier to be handling of the touch panel when mount to a device or maintenance.
However, such a touch panel disclosed in Japanese Patent Laid-open No. H9-50731 requires fitting accuracy between the recessed (female) fittings 7 embedded in the through-holes 4a, 4b, 4c, and 4d and other convex (male) fittings. More specifically, if the accuracy of position of the through-holes 4a, 4b, 4c, and 4d formed in the touch panel, the accuracy of inner diameter of the recessed (female) fittings 7, the accuracy of position of other convex (male) fittings, such as connector pins 12, provided in an interface so as to be fitted in the recessed (female) fittings 7, the accuracy of outer diameter of the other convex (male) fittings, or the accuracy of position of the touch panel mounted to a device is low, it will be difficult to fit the recessed (female) fittings 7 to other convex (male) fittings. As a result, it is impossible to mount the touch panel on a device properly and to connect the touch panel to the interface electrically. If the recessed (female) fittings 7 are forced to fit to other convex (male) fittings, stress is always applied to the touch panel, as a result, there is a possibility that the touch panel is deformed or cracked by an environmental resistance test (e.g., by temperature changes). In addition, there are also a possibilities that the touch panel is cracked due to repetition of attachment and detachment thereof and stable contact resistance is impaired.
On the other hand, even in a case where the recessed (female) fittings 7 are smoothly fitted to other convex (male) fittings, when contact between the recessed (female) fittings 7 and other convex (male) fittings is poor, stable contact resistance cannot be obtained.
There is a similar problem when convex (male) fittings 13 are embedded in the through-holes 4a, 4b, 4c, and 4d. 
The object of the present invention is to provide a touch panel which is capable of solving the above problem, and is capable of obtaining a stable contact resistance without being required of fitting accuracy.